1. Field of the Invention
This invention relates to a line light irradiating method and a line light source device for use in, for example, an operation for irradiating reading light to an image recording medium, on which image information has been recorded, in order to read out the recorded image information from the image recording medium. This invention particularly relates to a line light irradiating method and a line light source device, in which an electroluminescent layer is utilized. This invention also relates to an image information read-out method and apparatus utilizing the line light source device.
2. Description of the Related Art
Image information recording and read-out systems, in which electrostatic recording materials are utilized, have heretofore been proposed. With the proposed image information recording and read-out systems, such that a radiation dose delivered to an object during a medical X-ray image recording operation may be kept small, and such that the image quality of an image and its capability of serving as an effective tool in, particularly, the efficient and accurate diagnosis of an illness may be enhanced, a photo-conductive material sensitive to X-rays, such as a selenium plate constituted of, e.g., amorphous selenium (a-Se), is employed as an electrostatic recording material. The electrostatic recording material is exposed to radiation, such as X-rays, carrying radiation image information, and latent image charges carrying the radiation image information are thereby accumulated in the electrostatic recording material. Thereafter, the electrostatic recording material is scanned with a line light beam, which has been radiated out from a line light source, and currents occurring in the electrostatic recording material are detected via a striped electrode. In this manner, the electrostatic latent image represented by the latent image charges, i.e. the radiation image information, is read out. (The image information recording and read-out systems, in which the electrostatic recording materials are utilized, are described in, for example, U.S. Pat. No. 6,268,614.)
Also, image information recording and read-out systems, in which stimulable phosphor sheets are utilized as recording media, have heretofore been proposed. With the proposed image information recording and read-out systems, a stimulable phosphor sheet, on which radiation image information has been stored, is scanned with a line light beam, which has been radiated out from a line light source and which acts as reading light (stimulating rays) for causing the stimulable phosphor sheet to emit light in proportion to the amount of energy stored on the stimulable phosphor sheet during exposure of the stimulable phosphor sheet to radiation. Also, the light, which is emitted by the stimulable phosphor sheet when the stimulable phosphor sheet is exposed to the line light beam, is detected. In this manner, the image information, which has been stored on the stimulable phosphor sheet, is read out. As a detecting section for detecting the light emitted by the stimulable phosphor sheet, a photodiode image sensor, a charge coupled device (CCD) image sensor, or a panel-shaped or line-shaped detector, which is provided with a photo-conductive layer capable of exhibiting electrical conductivity when being exposed to the light emitted by the stimulable phosphor sheet. (The image information recording and read-out systems, in which the stimulable phosphor sheets are utilized as the recording media, are described in, for example, Japanese Unexamined Patent Publication No. 2000-338297.)
Further, in order for a read-out speed to be kept high, there has been proposed a scanning exposure apparatus, wherein a panel-shaped light source constituted of a plurality of line light sources, which are located at approximately identical pitches and in parallel with one another, is provided. With the proposed scanning exposure apparatus, line light beams are successively radiated out with different timing from the panel-shaped light source, and the scanning exposure with the line light beams is thereby performed. (The proposed scanning exposure apparatus provided with the panel-shaped light source is described in, for example, U.S. Pat. No. 6,376,857.) The proposed scanning exposure apparatus utilizes the line light sources, each of which comprises a light transmissive linear electrode, a planar electrode, and an electroluminescent (EL) layer located between the linear electrode and the planar electrode. Also, an electric current is successively caused to flow through the light transmissive linear electrodes of the line light sources, and the line light beams are thereby successively radiated out from the panel-shaped light source. As the material for the light transmissive linear electrodes, indium tin oxide (ITO) is utilized.
However, with the line light source utilizing the EL layer described above, the problems with regard to EL characteristics are encountered in that, as the cumulative period of actuation of the EL layer becomes long, in cases where predetermined electric power is supplied across the EL layer, the optical intensity of the line light beam radiated out from the EL layer becomes low.